The medal count officially began on Day 1 Saturday, as the first medals were awarded.
The first gold went to Ginny Thrasher of Springfield, Virginia, in shooting.
Here are four of the biggest Things to Watch during the Summer Games Saturday:
1) Women's 4x100m Freestyle Relay
Katie Ledecky had a shot at five medals at the Rio Olympics, but the women's 4x100-meter relay team finished second to Australia.
Despite finishing seventh in the 100-meter freestyle at the U.S. trials, Ledecky, from Bethesda, Maryland, was selected to anchor the relay at the Olympic Aquatics Stadium.
Amanda Weir will swam the leadoff leg, followed by Lia Neal, Allison Schmitt and Ledecky.
Ledecky made her Olympic debut in 2012 at 15 years old, winning gold in the women’s 800m freestyle by more than four seconds.
She went on to dominate the distance events over the next few years, becoming the first swimmer to win the 200m, 400m, 800m and 1500m freestyle titles at a single world championship in 2015.
Watch coverage of swimming on NBC4 or on your smartphone or desktop computer here.
2) Team USA Men’s Basketball Begins Quest for Gold
Led by an All-Star squad that includes Kevin Durant and Carmelo Anthony of Maryland, Team USA defeated China 119-62 in the first game for both squads.
Carmelo Anthony, already in possession of two gold medals and a bronze, looks to become the most decorated men’s basketball player in U.S. history as he participates in his fourth Olympic Games.
Durant picked up right where he left off in the 2012 Olympics with 25 points. The new Golden State Warriors star scored 30 points four years ago in the gold-medal game, when the Americans held off Spain for the championship. Only he and Anthony returned from that team, but the new guys were plenty ready for their Olympic moment.
"[Anthony's] going to be the leader of this team along with (Kevin Durant). And to have somebody who, this will be his fourth Olympics, that level of experience - and he's still a great player - and commitment, it's a godsend, really," U.S. coach Mike Krzyzewski said before the Olympic tournament began. "He'll be one of key factors in us attempting to win the gold medal."
DeMarcus Cousins added 17 points and Paul George 15 for the U.S., which is a heavy favorite to win a third straight gold and won't change any opinions after this performance.
Anthony finished with nine points and made by history becoming the first U.S. man to play basketball in four Olympics. He will become the first three-time gold medalist on the men's side if the U.S. wins. The 32-year-old veteran tied LeBron James and David Robinson by playing in his 24th game in the Olympics.
Former NBA lottery pick Yi Jianlian had 25 points to open his fourth Olympics. No other players were in double figures for the Asian champions.
Durant, Anthony, Cousins, Kyrie Irving and Klay Thompson started the game for the Americans, and all 12 players scored.
3) U.S. Women’s Soccer Takes on France
The U.S. women's soccer team is 2-0 in group play after beating France 1-0 Saturday afternoon. The team won its first game over New Zealand 2-0 Wednesday night.
The U.S. had two changes to its starting lineup from its first match with Crystal Dunn of the Washington Spirit replacing Mallory Pugh and Whitney Engen coming in for Julie Johnston, who was out with groin soreness.
The first real scoring chance went to France in the 16th minute as French captain Wendie Renard sent a header off the crossbar.
In the 30th minute, Tobin Heath provided the U.S.’s best chance at a goal in the first half as she struck a free kick that forced French goalkeeper Sarah Bouhaddi to tip the ball over the crossbar.
France looked strong throughout the first half and almost went up a goal late in the half on a shot from inside the box, but goalie Hope Solo was up to the challenge as the teams went into halftime scoreless.
The U.S. found more footing to start the second half, keeping more of the ball, putting more pressure on the French defense.
That pressure paid dividends in the 63rd minute as Carli Lloyd gave the U.S. the lead. After some good ball movement from the U.S., Heath got in open space on the left side of the box and sent in a shot that hit off the post. Lloyd was there to gather the rebound and knock it in to opening the scoring.
Following the goal, the U.S. made a defensive sub as Ali Krieger of the Washington Spirit came on for Dunn. Krieger, 32, became the oldest U.S. women’s soccer play to make her Olympic debut.
The team is also trying to become the first squad to win Olympic Gold after winning the World Cup, a feat they'll try to accomplish without retired veteran stars Abby Wambach and Lauren Holiday.
What the squad is missing in experience it makes up for in youth and exuberance. On Wednesday, 18-year-old Pugh started the game to become the youngest American women's player to start in an Olympic match.
The team also includes University of Virginia graduates Morgan Brian and Becky Sauerbrunn.
4) D.C. Fencer Kat Holmes Made Olympics Debut
D.C.'s Kat Holmes, who attended the National Cathedral School, made her debut in individual epee in fencing Saturday. She did not advance out of the round of 32, losing to Erika Kirpu, from Estonia, 5-4.
Holmes is still part of the women's team epee, which will compete Thursday.
Holmes, 21, started fencing at age 9. By 15, she had qualified for her first national team. She won individual and team titles at the Pan American Games in 2015.
Holmes studies neuroscience at Princeton University.